System for removing particles from a fluid by means of an electric field

ABSTRACT

A SYSTEM INCLUDING A CONDUIT COMPRISED OF SEVERAL SECTIONS OF ELECTRICALLY CONDUCTIVE PIPE ALTERNNATELY CONNECTED WITH PIPE OF ELECTRICAL INSULATION MATERIAL, A COMMON ELECTRICALLY CONDUCTIVE ROD EXTENDING ALONG THE CENTRAL AXIS OF THE CONDUIT, AND A DC POWER SUPPLY FOR SETTING UP A HIGH VOLTAGE NON-LINEAR FIELD BETWEEN THE COMMON ROD AS ONE ELECTRODE AND EACH CONDUCTIVE SECTION AS ANOTHER ELECTRODE, WHEREBY BOTH IONIZED AND NEUTRALPARTICLES IN A FLUID FLOWING THROUGH THE CONDUIT ARE ATTRACTED TO THE ELECTRODES AND DEPOSITED THEREON TO THE EXTENT THAT SHORT CIRCUIT CONDUCTION IS ESTABLISHED THROUGH THE DEPOSITS, CAUSING THE DEPOSITS TO BE FORCED FROM THE ELECTRODES AND CARRIED BY THE FLUID TO A SETTLING TANK FOR ACCUMULATION AND REMOVAL FROM THE SYSTEM.

6 m 1 RA 4 mH E, N 5 WA 7 NE 5 M 3 E m 4 Q N Filed Sept. 25, 1968 BY MEANS OF AN ELECTRIC FIELD April 20, 1971 35 Dc iWWW POWER SU PPLY VOLTAGE SENSING C. A. HARRIS SYSTEM FOR REMOVING PARTICLES FROM A FLUID VALVE CONTROL SYSTEM ATTORNEY United States Patent O 3,575,841 SYSTEM FOR REMOVING PARTICLES FROM A FLUID BY MEANS OF AN ELECTRIC FIELD Clarence A. Harris, Los Altos, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed Sept. 25, 1968, Ser. No. 762,460 Int. Cl. Btlld 13/02 US. Cl. 204299 7 Claims ABSTRACT OF THE DISCLOSURE A system including a conduit comprised of several sections of electrically conductive pipe alternately connected with pipe of electrical insulation material, a common electrically conductive rod extending along the central axis of the conduit, and a DC power supply for setting up a high voltage non-linear field between the common rod as one electrode and each conductive section as another electrode, whereby both ionized and neutral particles in a fluid flowing through the conduit are attracted to the electrodes and deposited thereon to the extent that short circuit conduction is established through the deposits, causing the deposits to be forced from the electrodes and carried by the fluid to a settling tank for accumulation and removal from the system.

BACKGROUND OF THE INVENTION The present invention relates to a system for removing particles from a fluid, and more particularly, it relates to an electric field system especially useful for removing both ionized and neutral particles from low conductivity water.

It is found that during operation of water-cooled electromagnets that deposits accumulate in the cooling tubes. These deposits accumulate even though the water used is distilled water which has been processed through deioniz ing filter beds to produce water with a resistance as high as ohms. This resistance is believed to be the practical limit obtainable with currently available equipment. Generally, deposits in the cooling tubes may be removed by periodically flushing the water passages with a mild acid to dissolve the deposits. Although acid flushing usually removes the deposits, the flushing may lead to a more serious condition in that it is diflicult to completely neutralize the acid, thereby leaving a residual acid in the system which may corrode the system components. Furthermore, acid flushing may be ineffective to clear water-cooling passages that have been completely plugged by the sloughing off of thick layers of deposits. It is also important to eliminate thin deposits from the water-cooling system so as not to increase the film temperature drop between the cooling water and the walls of the cooling passages. It is also important to prevent deposits of any kind from establishing an electrical leakage path across insulated water connections, especially in precision bending magnets such as used in conjunction with high energy linear accelerators where a variation in the magnet current would upset the precision field established in the magnet.

SUMMARY OF THE INVENTION In brief, the invention pertains to a system for continuously and automatically removing particles from a flowing fluid by means of a non-linear electric field established within an electrically conductive conduit section carrying the fluid. The field extends from the conductive section to an electrically conductive member centrally mounted within the conduit and electrically insulated therefrom. A direct current power source may be applied across the conductive section and the centrally mounted member for developing an electric field therebetween to Patented Apr. 20, 1971 cause both ionized and neutral particles in the fluid to deposit on the member and section. The deposits may be removed from the system with a surge current that forces or blows the deposits from the member and section when the deposits build to a point that short circuit conduction is established therebetween. A settling tank may be provided in series with the conduit for removal of the deposits from the system. Such a system may be used in conjunction with a low conductivity cooling-water system to maintain a water purity heretofore unknown; yet the apparatus is simple, low in cost, compact and may be easily installed for maintaining equipment that is in relatively inaccessible or remote locations free of deposits, in particular equipment located in a radiation environment where manual maintenance is unfeasible.

It is an object of the invention to remove both ionized and neutral particles from a fluid by means of an electric field.

Another object is to provide a simple, reliable, and compact apparatus for purifying low conductivity water.

Another object is to automatically remove deposits from electrodes of a fluid purifying system.

Other objects and advantageous features of the invention will be apparent in a description of a specific embodiment thereof, given by way of example only, to enable one skilled in the art to readily practice the invention, and described hereinafter with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The figure is a diagram of a system for removing particles from a fluid by means of a non-linear electric field, according to the invention.

DESCRIPTION OF AN EMBODIMENT Referring to the figure there is shown a system 10 for removing particles from a fluid by means of an electric field. The system includes a conduit comprised of a series of electrically conductive sections of pipe 12, 13, 14 and 15 which are alternately connected with electrical insulation sections of piping 18, 19, and 21. The electrical insulating sections should be constructed of a material that is electrically non-tracking to prevent establishment of electrical conduction paths following high voltage sparking. An electrically conductive member in the form of a rod 23 extends through one side of the section 12, which is an L-section, along the central axis of the conduit. The lower end of the conduit 15 is connected to a settling tank 25 which is comprised of an outer housing 27 made of electrical insulation material and a collection trough 29 which may be made of a pair of sides 30 of electrical insulation material which extend between opposing sides of the housing 27 and are secured to the lower part of the housing, leaving a space between the upper ends of the sides 30 and the housing 27. A support 31 extends from one of the sides 30 for maintaining the rod 23 in its central location within the conduit 11.

Each of the electrically conductive sections 13, 14 and 15 acts as an electrode while the common rod 23 constitutes an opposing electrode for each of the sections. When used in a low conductivity water-cooling system, all of the electrodes should be passivated.

Three non-linear transverse electric fields may be set up along the length of the conduit 11 by means of a DC power supply 33 having its positive terminal connected through a limiting resistor 35 to the common rod 23 and its negative terminal connected to ground. Each of the electrodes 13, 14 and 15 are connected respectively to ground through resistors 38, 39 and 40; these resistors may be used to establish voltages which may be monitored to determine the current flowing in each part of the circuit. Storage capacitors 43, 44 and 45 are connected between the common electrode 23 and the electrodes 13, 14 and 15, respectively.

In operation, the fluid from which particles are to be removed enters the system through the section 18, passing downward through the conduit 11 into the settling tank 25, with the processed fluid exiting through an outlet 47. As the fluid passes through the conduit 11, the nonlinear transverse electrical fields between the common electrode 23 and the electrodes 13, 14 and 15 cause both ionized and neutral particles in the fluid to migrate toward either the common electrode or the electrodes 13, 14 or 15, depending upon the nature of the particle.

Particles will deposit on the sections 13, 14 and 15 and the common electrode 23 eventually to the point that short circuit conduction will be established between one or all of the sections and the electrode 23. Under such conditions the capacitors 43, 44 and 45, which have been charged to the DC power supply voltage, will supply surge current through the deposits, causing the deposits to be blown from the electrodes and to be carried by the fluid to the settling tank 25. The limiting resistor 35 relieves the power supply from supplying the surge current and permits the necessary amount of surge current to be selected by the choice of values for the capacitors 43, 44 and 45 and the resistors 38, 39 and 40.

The particles blown from the electrodes are carried to the bottom of the trough 29 by gravity, while the fluid passes over the tops of the sides 30 to the outlet 47. Deposits accumulated in the bottom of the trough 29 may be removed through a drain 49 by means of a valve 51.

To make the system completely automatic, a voltage sensing and valve control system of conventional design may be provided for sensing the voltage drop which will appear across all of the capacitors 43, 44 and 45 whenever short circuit conditions are established between any set of electrodes. This will occur even though a short condition is established only between one set of electrodes. The other capacitors are across the shorted electrodes through their associated series resistor and the resistor associated with the shorted set. The voltage sensing and valve control system 53 may be made operable in response to the reduced voltage across the capacitors 43, 44 and 45, to temporarily open the valve 51 after a predetermined delay to permit flushing of the particles that would be blown oft due to the short circuit condition.

The provision of three electrically conductive sections is a convenient arrangement to enable monitoring of the effectiveness of particle removal adjacent the electrode 13. This could be done with a current meter connected through a selection switch to the lower end of each capacitor for comparing currents, and therefore, density of particles in the fluid adjacent the three electrodes. If there is no need to monitor the system, only one electrically conductive conduit section and capacitor, both connected directly to ground, is necessary.

The system described is particularly useful for removing from low conductivity water particles of a size that will pass through a 0.5 micron filter. The system is especially economical as compared to distilled water systems for maintaining large quantities of Water in a state of low conductivity and free of particulate matter. It is further envisioned that such a system might also find wide use in other applications, for example, as a water softening system for home water supplies, or on a larger scale, for industrial or domestic water supplies, or in a desalinization water supply system in conjunction with supplementary water purifying equipment. It is further anticipated that the subject invention should not be restricted to removing particles only from water, since particles in other low conductivity fluids are equally responsive to transverse electric fields.

A model exemplifying the invention was constructed having a conduit comprised of a stainless steel tube with an inner diameter of 0.5 inch and a stainless steel rod lying along the central axis of the stainless steel tube having an outer diameter of ,5 inch. A DC power supply of 1000 volts was connected across the tube and conduit electrodes and low conductivity water having a resistance of 10 ohm-cm. was passed therebetween at the rate of one gallon per minute. A one microfarad capacitor was connected across the electrodes. The deposits accumulated on the electrodes to the point that a bridge was created between the electrodes, causing a surge current from the capacitor to force the deposits from the electrodes.

While an embodiment of the invention has been shown and described, further embodiments or combinations of those described herein will be apparent to those skilled in the art without departing from the spirit of the invention or from the scope of the appended claims.

What is claimed is:

1. In a system for removing particles from a flowing fluid by means of a non-linear electric field, the combination of:

(a) a conduit through which said fluid flows, said conduit comprising a plurality of electrically conductive sections and a plurality of electrical insulation sections alternately connected to form said conduit, said conduit constituting a first electrode;

(b) an electrically conductive member centrally mounted within said conduit and electrically insulated therefrom and constituting a second electrode; and

(c) a direct current power source applied across said first and second electrodes for developing an electric field therebetween for causing the particles in the fluid to migrate to said electrodes and to build deposits thereon, said source being eifective for supplying a current surge to said electrodes for removing said deposits upon the building of the deposits to a predetermined spacing therebetween.

2. The combination of claim 1, wherein:

said power source includes a storage capacitor across said electrodes for supplying a current surge upon said deposits building to the point that a short circuit path is established therethrough,

said current surge causing the deposits to be forced from the electrodes.

3. The combination of claim 1, further including a settling tank in series with said conduit for collecting the deposits forced from said electrodes.

4. The combination of claim 3, further including means responsive to said current surge for removing the collected deposits in said settling tank.

5. The combination of claim 1, wherein said centrally mounted member is a rod extending along the central axis of said conduit, and said conduit terminates at one end with an electrically conductive L-section through which said rod extends.

6. The combination of claim 1, wherein said electrically conductive sections have an outer diameter that is less than the inner diameter of said insulation sections to inhibit accumulation of said deposits on said insulation sections.

7. The combination of claim 1, further including means connected to said plurality of electrically conductive sections for establishing a plurality of voltages, each voltage representing the density of particles in the fluid adjacent one of said electrically conductive sections for monitoring the effectiveness of said system.

References Cited UNITED STATES PATENTS 1,555,231 9/ 1925 Skaer 204299X 1,931,725 10/ 1933 Girvin 204299X 2,665,246 1/ 1954 Bates 204-299X 3,423,306 1/1969 HurWitz et a1. 204299 HOWARD S. WILLIAMS, Primary Examiner D. R. VALENTINE, Assistant Examiner 

